Op, not to scare you but I had a similar thing with my own cat a few years ago. A long labour, seemed to still be pregnant but no more births. If turns out that her birth canal had collapsed. I’m not sure if it was connected but then she actually never started lactating!

The whole thing was petrifying but definitely keep in touch with the vet!

There are multiple different types of anaesthetic for cats - what happens if she needs a csection - it’s irresonsible to allow her to breed repeatedly. And as she has other kittens inside and they don’t come she will need surgery to remove them and potentially they and her could die if she is just left?

If she is entire then she should be inside and away from males. Do you even know who the father of the kittens are?